x1, y1, x2, y2 = map(float, input().split())
print(abs(complex(x1-x2, y1-y2)))
 x1, y1, x2, y2 = map(float, input().split()) x1 map(float, input().split()) map float input().split() ().split () input split y1 x2 y2 print(abs(complex(x1-x2, y1-y2))) print abs(complex(x1-x2, y1-y2)) abs complex(x1-x2, y1-y2) complex x1-x2 x1 x2 y1-y2 y1 y2 x2, y2 = map(float, input().split()) map(float, input().split()) x2 y2 = map(float, input().split()) map(float, input().split()) y2 x1, y1, x2, y2 = map(float, input().split()) map(float, input().split()) x1 y1, x2, y2 = map(float, input().split()) map(float, input().split()) y1
x1, y1, x2, y2 = map(float, input().split())
print(abs(complex(x1-x2, y1-y2)))

